Quantitative characterization of SWNT dispersions

Quantitative characterization of single walled carbon nanotube (SWNT) dispersions is critical for developing various SWNT-based applications, e.g., transparent conducting thin films, SWNT thin film transistors and SWNT-reinforced composites. Quantified structural information of SWNTs in the dispersions prepared under various conditions, like length, bundle diameter, degree of exfoliation, etc., is valuable for establishing the processing-structure-propertyperformance relationships of SWNT based composites. Moreover, it also provides a measure for quality control of various SWNT processing techniques. In this paper, we will introduce two different characterization techniques, preparative ultracentrifuge method and simultaneous Raman scattering and photoluminescence spectroscopy, for quantifying the structural information of various SWNT dispersions. The former method allows for determination of the transport properties, namely, bulk averaged sedimentation and diffusion coefficients of SWNT particles in a dispersion, and thus to extract their averaged length and bundle diameter. The latter technique is able to reveal the degree of exfoliation of SWNT bundles under various processing conditions.